Aerosol generating device, control method and storage medium

ABSTRACT

An aerosol generating device includes a power supply that supplies electric power to a heating unit, and a control unit that controls the supply of electric power in accordance with a control sequence consisting of sections including a first section and a second section. The control sequence designates a first time length for the first section and a second time length for the second section. The control unit terminates the first section when the temperature of the heating unit has reached a predetermined temperature and, in a case of terminating the first section earlier than a first time point, continues the second section over a total time of a residual time until the first time point and the second time length.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priorities to International PatentApplication No. PCT/JP2022/006894 filed on Feb. 21, 2022 and JapanesePatent Application No. 2021-076017 filed on Apr. 28, 2021, both of whichare incorporated herein by references.

BACKGROUND OF THE INVENTION Technical Field

This disclosure relates to an aerosol generating device, a controlmethod and a storage medium.

Related Art

An electric heating type aerosol generating device that generatesaerosol by heating an aerosol source and delivers the generated aerosolto a user is known. For example, an electronic cigarette is a kind ofthe above-described aerosol generating device. The electronic cigaretteimparts a flavor component to generated aerosol to let the user inhalethe aerosol.

SUMMARY

According to an aspect, there is provided an aerosol generating devicethat includes: a heating unit configured to generate aerosol by heatingan aerosol source; a power supply configured to supply electric power tothe heating unit; and a control unit configured to control the supply ofelectric power from the power supply to the heating unit in accordancewith a control sequence that consists of a plurality of sectionsincluding: a first section for changing a temperature of the heatingunit from a first temperature toward a second temperature, and a secondsection, which follows the first section, for maintaining thetemperature of the heating unit, wherein the control sequence designatesa first time length for the first section and a second time length forthe second section, the control unit is configured to terminate thefirst section when the temperature of the heating unit has reached thesecond temperature, and the control unit is configured to, in a case ofterminating the first section earlier than a first time point at whichthe first time length elapses from the start of the first section,continue the second section over a total time of a residual time untilthe first time point and the second time length.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the outer appearance of an aerosolgenerating device according to an embodiment;

FIG. 2 is an explanatory diagram for explaining the insertion of atobacco stick into the aerosol generating device shown in FIG. 1 ;

FIG. 3 is a block diagram showing an example of a general circuitconfiguration of the aerosol generating device shown in FIG. 1 ;

FIG. 4 is a block diagram showing an example of the configuration of ameasurement circuit to be used to measure the temperature of a heatingunit;

FIG. 5 is an explanatory diagram for explaining a measurement period anda PWM control period during a heating period;

FIG. 6 is an explanatory diagram for explaining an example of thepositional relationship between the heating unit and a thermistor;

FIG. 7 is an explanatory diagram for explaining a temperature profileand a heating profile according to an embodiment;

FIG. 8 is an explanatory diagram showing an example of a temperatureprofile in a case where a residual time is added to the time length of asubsequent section because the end of a temperature fall section isearlier than a predetermined time;

FIG. 9 is an explanatory diagram for explaining the relationship betweena first temperature index and a second temperature index;

FIG. 10 is an explanatory diagram showing two examples of thetemperature profile in a case where a target temperature of thesubsequent section is reset to the temperature at the terminating pointin time of the temperature fall section;

FIG. 11 is an explanatory diagram showing an example of the temperatureprofile in a case where the subsequent section is shortened because theend of the temperature fall section is later than a predetermined timein the first modification;

FIG. 12 is an explanatory diagram showing an example of the temperatureprofile in a case where the subsequent section is shortened because theend of the temperature fall section is later than a predetermined timein the second modification;

FIG. 13 is an explanatory diagram showing an example of the temperatureprofile in a case where the subsequent section is skipped and the nextsubsequent section is shortened because the end of the temperature fallsection is much later than a predetermined time in the firstmodification;

FIG. 14 is an explanatory diagram showing an example of the temperatureprofile in a case where the subsequent section is skipped and the nextsubsequent section is shortened because the end of the temperature fallsection is much later than a predetermined time in the secondmodification;

FIG. 15 is an explanatory diagram showing an example of the temperatureprofile in a case where the target temperature of atemperature-maintaining section before termination is reset to thetemperature at a reference point in time;

FIG. 16 is an explanatory diagram showing an example of the temperatureprofile including a recovery section according to the thirdmodification;

FIG. 17A is an explanatory diagram showing the first example of theconfiguration of profile data describing the heating profile;

FIG. 17B is an explanatory diagram showing the second example of theconfiguration of the profile data describing the heating profile;

FIG. 18 is a flowchart showing an example of the overall flow of anaerosol generation process according to an embodiment;

FIG. 19 is a flowchart showing an example of a flow of a temperaturecontrol process for a PID control section shown in FIG. 18 ;

FIG. 20A is a flowchart showing the first example of a flow of atemperature control process for an OFF section shown in FIG. 18 ;

FIG. 20B is a flowchart showing the second example of a flow of thetemperature control process for the OFF section shown in FIG. 18 ;

FIG. 20C is a flowchart showing the third example of a flow of thetemperature control process for the OFF section shown in FIG. 18 ;

FIG. 21 is a flowchart showing an example of a flow of an enddetermination process for a preheating temperature rise section;

FIG. 22 is a flowchart showing an example of a flow of an enddetermination process for a temperature fall section; and

FIG. 23 is a flowchart showing an example of a flow of a controlparameter selection process after the end of the temperature fallsection.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention, and limitation is not madean invention that requires a combination of all features described inthe embodiments. Two or more of the multiple features described in theembodiments may be combined as appropriate. Furthermore, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

<<1. Configuration Example of Device>>

In this specification, an example in which the technology according tothe present disclosure is applied to a non-combustion-type device thatgenerates aerosol by atomizing an aerosol source by heating it withoutcombustion will mainly be explained. A device like this is also called areduced-risk product (RRP) or is simply called an electronic cigarette.However, technology according to the present disclosure is not limitedto this example and can be applied to an aerosol generating device ofany kind such as a combustion-type device or a medical nebulizer.

<<1-1. Outer Appearance>>

FIG. 1 is a perspective view showing the outer appearance of an aerosolgenerating device 10 according to an embodiment. FIG. 2 is anexplanatory diagram for explaining the insertion of a tobacco stick intothe aerosol generating device 10 shown in FIG. 1 . Referring to FIG. 1 ,the aerosol generating device 10 includes a main body 101, a front panel102, a display window 103, and a slider 104.

The main body 101 is a housing internally supporting one or more circuitboards of the aerosol generating device 10. In this embodiment, the mainbody 101 has a substantially cuboidal rounded shape elongated in thevertical direction of the drawing. The size of the main body 101 can bea size which the user can grasp with one hand. The front panel 102 is aflexible panel member covering the front surface of the main body 101.The front panel 102 can be detachable from the main body 101. The frontpanel 102 also functions as an input unit for accepting a user input.For example, when the user pushes the center of the front panel 102, abutton (not shown) disposed between the main body 101 and the frontpanel 102 is pressed, so a user input can be detected. The displaywindow 103 is a band-like window extending along the longitudinaldirection in substantially the center of the front panel 102. Thedisplay window 103 transmits light generated by one or more lightemitting diodes (LEDs) arranged between the main body 101 and the frontpanel 102 to the outside.

The slider 104 is a cover member slidably disposed along a direction 104a on the upper surface of the main body 101. As shown in FIG. 2 , whenthe slider 104 is slid to the near side of the drawing (that is, whenthe slider 104 is opened), an opening 106 in the upper surface of themain body 101 is exposed. When inhaling aerosol by using the aerosolgenerating device 10, the user inserts a tobacco stick 15 into a tubularinsertion hole 107 along a direction 106 a from the opening 106 exposedby opening the slider 104. A section perpendicular to the axialdirection of the insertion hole 107 can be, for example, circular,elliptical, or polygonal, and the sectional area of the sectiongradually reduces toward the bottom surface. Accordingly, the innersurface of the insertion hole 107 pushes the outer surface of thetobacco stick 15 inserted into the insertion hole 107, therebypreventing a fall of the tobacco stick 15 by the frictional force. Thisalso increases the efficiency of heat transfer from a heating unit 130(to be described later) to the tobacco stick 15. When the user finishesinhaling aerosol, he or she pulls out the tobacco stick 15 from theinsertion hole 107, and closes the slider 104.

The tobacco stick 15 is a tobacco article holding a filler inside acylindrical rolling paper. The filler of the tobacco stick 15 can be,for example, a mixture of an aerosol generating substrate and shreddedtobacco. As the aerosol generating substrate, it is possible to use asubstrate containing an aerosol source of any kind, such as glycerin,propylene glycol, triacetin, 1,3-butanediol, or a mixture thereof. Theshredded tobacco is a so-called flavor source. The material of theshredded tobacco can be, for example, a lamina or a backbone. Note thata flavor source not originating from tobacco may also be used instead ofthe shredded tobacco.

<1-2. Circuit Configuration>

FIG. 3 is a block diagram showing an example of a general circuitconfiguration of the aerosol generating device 10. Referring to FIG. 3 ,the aerosol generating device 10 includes a control unit 120, a storageunit 121, an input detection unit 122, a state detection unit 123, aninhalation detection unit 124, a light emitting unit 125, a vibrationunit 126, a communication interface (I/F) 127, a connection I/F 128, aheating unit 130, a first switch 131, a second switch 132, a battery140, a booster circuit 141, a residual amount meter 142, a measurementcircuit 150, and a thermistor 155.

The control unit 120 can be a processor such as a central processingunit (CPU) or a microcontroller. The control unit 120 controls allfunctions of the aerosol generating device 10 by executing computerprograms (also called software or firmware) stored in the storage unit121. The storage unit 121 can be a semiconductor memory or the like. Thestorage unit 121 stores one or more computer programs, and various data(for example, profile data 51 describing a heating profile 50) to beused for heating control (to be described later).

The input detection unit 122 is a detection circuit for detecting a userinput. For example, the input detection unit 122 detects pushing of thefront panel 102 (that is, pressing of a button) by the user, and outputsan input signal indicating the detected state to the control unit 120.Note that the aerosol generating device 10 can include an input deviceof any kind such as a button, a switch, or a touch-sensitive screen,instead of (or in addition to) the front panel 102. The state detectionunit 123 is a detection circuit for detecting an open/closed state ofthe slider 104. The state detection unit 123 outputs a state detectionsignal indicating whether the slider 104 is open or closed to thecontrol unit 120. The inhalation detection unit 124 is a detectioncircuit for detecting inhalation (puff) of the tobacco stick 15 by theuser. As an example, the inhalation detection unit 124 can include athermistor (not shown) disposed near the opening 106. In this case, theinhalation detection unit 124 can detect inhalation by the user based ona change in resistance value of the thermistor resulting from atemperature change caused by the inhalation. As another example, theinhalation detection unit 124 can include a pressure sensor (not shown)disposed on the bottom of the insertion hole 107. In this case, theinhalation detection unit 124 can detect inhalation based on a reductionin atmospheric pressure resulting from an air current caused by theinhalation. The inhalation detection unit 124 outputs, for example, aninhalation detection signal indicating whether inhalation is performed,to the control unit 120.

The light emitting unit 125 includes one or more LEDs, and a driver fordriving the LEDs. The light emitting unit 125 turns on each LED inaccordance with an instruction signal input from the control unit 120.The vibration unit 126 includes a vibrator (e.g., an eccentric motor)and a driver for driving the vibrator. The vibration unit 126 vibratesthe vibrator in accordance with an instruction signal input from thecontrol unit 120. The control unit 120 can use one or both of the lightemitting unit 125 and the vibration unit 126 by any pattern, in order tonotify the user of a certain status (for example, the progress of asession) of the aerosol generating device 10. For example, the lightemission patterns of the light emitting unit 125 can be distinguished byelements such as the light emission state (always on/blinking/off), theblinking period, and the light color of each LED. The vibration patternsof the vibration unit 126 can be distinguished by elements such as thevibration state (vibration/stop) and the vibration strength of thevibrator.

The wireless I/F 127 is a communication interface by which the aerosolgenerating device 10 wirelessly communicates with another device (forexample, a personal computer (PC) or a smartphone owned by the user).The wireless I/F 127 can be an interface complying with a wirelesscommunication protocol such as Bluetooth®, near field communication(NFC), or a wireless local area network (LAN). The connection I/F 128 isa wired interface having a terminal for connecting the aerosolgenerating device 10 to another device. The connection I/F 128 can be auniversal serial bus (USB) interface or the like. The connection I/F 128can also be used to charge the battery 140 from an external power supply(via a feeder line (not shown)).

The heating unit 130 is a resistive heat generating part that generatesaerosol by heating an aerosol source included in an aerosol generatingsubstrate of the tobacco stick 15. As a resistive heat generatingmaterial of the heating unit 130, it is possible to use a mixture of oneof more of copper, a nickel alloy, a chromium alloy, stainless steel,and platinum rhodium. One terminal of the heating unit 130 is connectedto the positive electrode of the battery 140 via the first switch 131and the booster circuit 141, and the other terminal of the heating unit130 is connected to the negative electrode of the battery 140 via thesecond switch 132. The first switch 131 is a switching element disposedin a feeder line between the heating unit 130 and the booster circuit141. The second switch 132 is a switching element disposed in a groundline between the heating unit 130 and the battery 140. The first switch131 and the second switch 132 can be, for example, field effecttransistors (FETs).

The battery 140 is a power supply for supplying electric power to theheating unit 130 and other constituent elements of the aerosolgenerating device 10. FIG. 3 does not show feeder lines from the battery140 to the constituent elements except the heating unit 130. The battery140 can be, for example, a lithium-ion battery. The booster circuit(DC/DC converter) 141 is a voltage conversion circuit for amplifying thevoltage of the battery 140 in order to feed the heating unit 130. Theresidual amount meter 142 is an IC chip for monitoring the residualpower amount and other statuses of the battery 140. The residual amountmeter 142 can periodically measure the status values of the battery 140,such as the state of charge (SOC), the state of health (SOH), therelative SOC (RSOC), and the power supply voltage, and can output themeasurement results to the control unit 120.

When a user input requesting the start of heating is detected, thecontrol unit 120 starts to cause electric power to be supplied from thebattery 140 to the heating unit 130. This user input can be, forexample, long press of a button to be detected by the input detectionunit 122. The control unit 120 can cause electric power to be suppliedfrom the battery 140 to the heating unit 130 at a voltage amplified bythe booster circuit 141 by outputting control signals to the firstswitch 131 and the second switch 132 to turn on the two switches. In acase where the first switch 131 and the second switch 132 are FETs, thecontrol signals to be output from the control unit 120 to the twoswitches are control pulses to be applied to the gates of theseswitches. In temperature control to be described below, the control unit120 adjusts the duty ratio of these control pulses by pulse widthmodulation (PWM). Note that the control unit 120 can also use pulsefrequency modulation (PFM) instead of PWM.

<1-3. Measurement of Heater Temperature>

In this embodiment, the control unit 120 controls the supply of electricpower from the battery 140 to the heating unit 130 so as to implement adesired temperature profile for providing a good user experiencethroughout the whole heating period including a preheating period and aninhalable period. This control can mainly be feedback control using atemperature index having a correlation with the temperature of theheating unit 130 as a controlled variable, and the duty ratio of PWM asa manipulated variable. Assume that PID control is adopted as thisfeedback control. In this embodiment, the aerosol generating device 10has two types of measurement units for measuring the temperature indexof the heating unit 130. The measurement circuit 150 shown in FIG. 3 isone of the two types of measurement units, and measures a firsttemperature index based on the electrical resistance value of theheating unit 130. The other measurement unit is the thermistor 155 to beexplained later.

FIG. 4 is a block diagram showing an example of the configuration of themeasurement circuit 150 shown in FIG. 3 . Referring to FIG. 4 , themeasurement circuit 150 includes divider resistors 151, 152, and 153,and an operational amplifier 154. One terminal of the divider resistor151 is connected to a power supply voltage VTEMP, and the other terminalis connected to one terminal of the divider resistor 152. The otherterminal of the divider resistor 152 is grounded. The contact betweenthe divider resistor 151 and the divider resistor 152 is connected to aterminal ADC_VTEMP of the control unit 120. An input to the terminalADC_VTEMP indicates a reference value for resistance value measurement.One terminal of the divider resistor 153 is connected to the powersupply voltage VTEMP, and the other terminal is connected to the feederline of the heating unit 130. The contact between the divider resistor153 and the feeder line of the heating unit 130 is connected to a firstinput terminal of the operational amplifier 154. A second input terminalof the operational amplifier 154 is grounded. An output terminal of theoperational amplifier 154 is connected to a terminal ADC_HEAT_TEMP ofthe control unit 120. An input to the terminal ADC_HEAT_TEMP indicates avalue that changes due to an electrical resistance value Rh depending onthe temperature of the heating unit 130. The control unit 120 cancalculate the electrical resistance value Rh of the heating unit 130based on the ratio of the value input to the terminal ADC_HEAT_TEMP tothe value (reference value) input to the terminal ADC_VTEMP.

The electrical resistance value of the heating unit 130 has, forexample, the characteristic that the value monotonously increases as thetemperature rises (that is, the value has a correlation to thetemperature). In this embodiment, therefore, the control unit 120 usesthe electrical resistance value of the heating unit 130, which iscalculated by using the measurement circuit 150, as a temperature index(first temperature index) as the controlled variable of PID control.Note that the control unit 120 may, of course, further convert thecalculated electrical resistance value into a temperature by using aresistance-temperature coefficient, and use the derived measuredtemperature as the controlled variable of PID control.

<1-4. Temperature Control>

In this embodiment as described above, temperature control of theheating unit 130 is mainly performed by the method of deciding the dutyratio of PWM of electric power to be supplied to the heating unit 130.Letting R_(TGT) [Ω] be the target value (the resistance valuecorresponding to the target temperature) of PID control, and R(n) [Ω] bethe value (measured resistance value) of the first temperature index ina current control cycle n (n is an integer), a duty ratio D(n) of thecontrol cycle n can be derived in accordance with, for example, equation(1) below:

D(n)={K _(p)×(R _(TGT) −R(n))+K _(i)×Σ₀ ^(n)(R _(TGT) −R(k))−K_(d)×(R(n)−R(n−1))}/1000  (1)

In equation (1), K_(p), K_(i), and K_(d) respectively represent aproportional gain, an integral gain, and a differential gain. Note thatin the second term on the right side as an integral term, saturationcontrol can be applied to a cumulative value of a deviation of the indexvalue with respect to the target value. In this case, if the cumulativevalue is larger than a predetermined upper limit value, the cumulativevalue is substituted by the upper limit value; and if the cumulativevalue is smaller than a predetermined lower limit value, the cumulativevalue is substituted by the lower limit value.

To enable feedback control during the heating period in this embodiment,the control unit 120 sets a part of repetitive control cycles as ameasurement period for measuring the first temperature index, and setsthe remainder of the control cycles as a PWM control period forperforming PWM control. FIG. 5 is an explanatory diagram for explainingthe measurement period and the PWM control period during the heatingperiod. In FIG. 5 , the abscissa represents the time, and the ordinaterepresents the voltage to be applied to the heating unit 130. Onecontrol cycle during the heating period includes a measurement period 20at the beginning and a PWM control period 30 as the remainder. In thisexample shown in FIG. 5 , a period from t0 to t1 is the measurementperiod 20 of one control cycle, and a period from t1 to t2 is the PWMcontrol period 30 of the same control cycle. Likewise, a period from t2to t3 is the measurement period 20 of the next one control cycle, and aperiod from t3 to t4 is the PWM control period 30 of the same controlcycle. The length of one control cycle is equivalent to the periodicityof measurement of the first temperature index, and can be, for example,tens of milliseconds.

In the control cycle n, the control unit 120 applies a very short pulse21 (for example, the pulse width is 2 ms) to the heating unit 130 aplurality of times (for example, 8 times) during the measurement period20, and obtains the average value of resistance values calculated aplurality of times by using the measurement circuit 150 during onemeasurement period 20 as the measured value R(n) of the firsttemperature index. By using the measured value R(n), the control unit120 calculates the duty ratio D(n) of PWM in the control cycle n inaccordance with the above-described control equation. Then, in the PWMcontrol period 30, the control unit 120 applies a pulse 31 having apulse width W1 equivalent to the product of a length W0 of this periodand the duty ratio D(n) to the heating unit 130 (that is, outputscontrol pulses having the same pulse width W1 to the first switch 131and the second switch 132). The temperature of the heating unit 130 isso controlled as to approach the target value by repeating the feedbackcontrol as described above.

<1-5. Introduction of Auxiliary Thermistor>

The above-described control cycle can be kept repeated by periodicallysetting the measurement period 20 throughout the whole heating period.However, the method of applying pulses to the heating unit 130 duringthe measurement period 20 raises the temperature of the heating unit 130and consumes the residual battery amount, although the pulse width isshort. Meanwhile, a desired temperature profile of the heating unit 130may include a period in which the temperature of the heating unit 130,which is once raised to a high value, is decreased to a lower value.During this period, it is advantageous to apply no pulses to the heatingunit 130 at all in order to efficiently lower the temperature of theheating unit 130. However, if no pulses are applied to the heating unit130 at all, the first temperature index cannot be measured by using themeasurement circuit 150. As generally shown in FIG. 3 , therefore, theaerosol generating device 10 according to this embodiment furtherincludes the thermistor 155. The thermistor 155 is disposed near theheating unit 130, and outputs a value depending on the temperature ofthe heating unit 130 to the control unit 120. In a section in which thetemperature of the heating unit 130 is decreased, the control unit 120determines a timing at which this section is terminated, by using thesecond temperature index based on the output value from the thermistor155 (for example, by comparing the index value with the target value).On the other hand, in other sections, the control unit 120 controls thesupply of electric power from the battery 140 to the heating unit 130 byusing the first temperature index based on the electrical resistancevalue of the heating unit 130, as described above. The periodicity ofmeasurement of the second temperature index can be, for example, tens ofmilliseconds to hundreds of milliseconds.

FIG. 6 shows an example of the positional relationship between theheating unit 130 and the thermistor 155, when viewed in the direction106 a shown in FIG. 2 (the axial direction of the insertion hole 107).In this example shown in FIG. 6 , a cylindrical member 130 a is a memberdefining the space of the insertion hole 107 for receiving the tobaccostick 15. The cylindrical member 130 a is formed by using a materialhaving a high thermal conductivity, such as stainless steel (SUS) oraluminum. A film heater 130 b is so wound as to surround the outercircumferential surface of the cylindrical member 130 a. The film heater130 b is formed by a pair of films having a high heat resistance andhigh insulation properties, and a resistive heat generating materialsandwiched between these films. The heating unit 130 is formed by thecylindrical member 130 a and the film heater 130 b described above, anda Joule heat generated by an electric current flowing through the filmheater 130 b heats the tobacco stick 15 inserted into the insertion hole107 via the cylindrical member 130 a. In addition, a heat insulatingmember 108 is so wound as to surround the outer circumferential surfaceof the film heater 130 b. The heat insulating member 108 is formed byglass wool or the like, and protects the constituent elements of theaerosol generating device 10 from the heat of the heating unit 130. Thethermistor 155 is disposed outside the heat insulating member 108. Thesurface of the film heater 130 b is normally smooth, so positioningoften becomes difficult if the thermistor 155 is disposed on the outercircumferential surface of the film heater 130 b. However, when thethermistor 155 is disposed on the outer circumferential surface of theheat insulating member 108 formed by glass wool, it becomes easy toposition the thermistor 155, and a control circuit connected to thethermistor 155 is well protected. However, the positional relationshipin which the heat insulating member 108 is disposed between the heatingunit 130 and the thermistor 155 causes the second temperature indexbased on the output value from the thermistor 155 to follow thetemperature change of the heating unit 130 with a certain delay.

<1-6. Temperature Profile and Heating Profile>

The control unit 120 executes temperature control of the heating unit130 in accordance with the heating profile as a control sequencedefining temporal changes in control conditions for implementing adesired temperature profile. In this embodiment, the heating profileincludes a plurality of sections temporally dividing the heating period,and designates specifications of temperature control of each section bya target value and other control parameters.

FIG. 7 is an explanatory diagram for explaining the temperature profileand the heating profile adoptable in this embodiment. In FIG. 7 , theabscissa represents the elapsed time from the start of power supply tothe heating unit 130, and the ordinate represents the temperature of theheating unit 130. A thick line represents a temperature profile 40 as anexample. The temperature profile 40 includes a preheating period (T0 toT2) at the beginning, and an inhalable period (T2 to T8) following thepreheating period. As an example, the whole length of the inhalableperiod can be about five minutes, and the user can perform inhalationmore than 10 times during the inhalable period.

The preheating period includes a temperature rise section (T0 to T1) inwhich the temperature of the heating unit 130 is rapidly raised from anenvironmental temperature H0 to a first temperature H1, and amaintaining section (T1 to T2) in which the temperature of the heatingunit 130 is maintained at the first temperature H1. By thus rapidlyheating the heating unit 130 to the first temperature H1 at thebeginning, it is possible to sufficiently spread heat to the wholeaerosol generating substrate of the tobacco stick 15 in an early stage,and start providing the user with high-quality aerosol more rapidly.

The inhalable period includes a maintaining section (T2 to T3) in whichthe temperature of the heating unit 130 is maintained at the firsttemperature H1, a temperature fall section (T3 to T4) in which thetemperature of the heating unit 130 is lowered to a second temperatureH2, and a maintaining section (T4 to T5) in which the temperature of theheating unit 130 is maintained at the second temperature H2. Since thetemperature of the heating unit 130, which is once raised to the firsttemperature H1, is lowered to the second temperature H2 as describedabove, it is possible to stably provide the user with inhalation with agood tobacco flavor for a longer time. The inhalable period furtherincludes a temperature rise section (T5 to T6) in which the temperatureof the heating unit 130 is gradually raised from the second temperatureH2 to a third temperature H3, a maintaining section (T6 to T7) in whichthe temperature of the heating unit 130 is maintained at the thirdtemperature H3, and a temperature fall section (T7 to T8) in which thetemperature of the heating unit 130 is lowered to the environmentaltemperature H0. Since the temperature of the heating unit 130 is againraised in the second half of the inhalable period as described above, itis possible to suppress a decrease in tobacco flavor in a situation inwhich the amount of the aerosol source included in the tobacco stick 15decreases, and provide the user with a highly satisfactory experience tothe end of the inhalable period.

For example, the first temperature H1, the second temperature H2, andthe third temperature H3 can be 295° C., 230° C., and 260° C.,respectively. However, it is also possible to design a differenttemperature profile in accordance with, for example, a design guidelineof a manufacturer, user preference, or characteristics of each type of atobacco article.

The heating profile 50 includes eight sections S0 to S7 bounded by T1 toT7. As will be explained later, however, the transition timing betweentwo sections does not necessarily match one of the points in time T1 toT7 shown in the drawing, but follows a termination condition designatedfor each section. The heating profile 50 defines one or more controlparameters, which are enumerated below for each of the sections S0 toS7:

-   -   “Section type”    -   “Target temperature”    -   “Target temperature resistance value”    -   “PID control type”    -   “Gains”    -   “Time length”    -   “Termination condition”

“Section type” is a parameter for designating whether the correspondingsection is a PID control section or an OFF section. The PID controlsection is a section in which PID control is performed based on thefirst temperature index calculated by the control unit 120 by using themeasurement circuit 150. The OFF section is a section in which thecontrol unit 120 stops power supply to the heating unit 130 withoutperforming PID control.

“Target temperature” is a parameter for designating the temperature ofthe heating unit 130, which should be reached at the end of thecorresponding section. “Target temperature resistance value” is aparameter for designating a value obtained by converting the value of“target temperature” into a resistance value. For example, a targettemperature H_(TGT) [° C.] can be converted into the target temperatureresistance value R_(TGT) [Ω] in accordance with equation (2) below:

R _(TGT)=(P _(TGT) −P _(ENV))·α·R _(ENV) +R _(ENV)  (2)

In equation (2), H_(ENV) represents a reference environmentaltemperature, a represents the temperature-resistance coefficient of theresistive heat generating material of the heating unit 130, and R_(ENV)represents an electrical resistance value at the reference environmentaltemperature. The values of H_(ENV), a, and R_(ENV) are measured orderived by an evaluation test in advance and prestored in the storageunit 121.

“PID control type” is a parameter for designating whether to constantlymaintain the target value at the value of “target temperature resistancevalue” throughout the PID control section, or linearly change the targetvalue by linear interpolation. If “PID control type” is “constant”, thecontrol unit 120 performs feedback control while keeping the targetvalue of temperature control constant in the corresponding section. If“PID control type” is “linear interpolation”, the control unit 120performs feedback control while changing the target value of temperaturecontrol step by step in the corresponding section. The control targetvalue in “linear interpolation” can be set at a specific start value(for example, a currently-measured value or a target value of animmediately preceding section) at the beginning of the section, andincreased or decreased practically linearly (in practice, step by stepfor each control cycle) so that the value becomes “target temperatureresistance value” at the end of the section. “PID control type” and“section type” can also be regarded as parameters for designating acontrol method to be applied to temperature control in each section.

“Gains” is a set of parameters for designating the values of theproportional gain K_(p), the integral gain and the differential gainK_(d) for the PID control section. Note that when a gain value differentfrom a gain value designated in a preceding section is designated in acertain PID control section, the cumulative deviation of the integralterm (the second term on the right side of equation (1)) of feedbackcontrol may be reset.

“Time length” is a parameter for designating a predefined temporallength for each section. “Termination condition” is a parameter fordesignating a condition for terminating temperature control in eachsection (that is, a condition for transitioning temperature control tothe next section). For example, “termination condition” can be one ofC1, C2, and C3 below:

-   -   C1: Elapse of time designated by “time length”    -   C2: Arrival of a temperature index at a resistance value        designated by “target temperature resistance value”    -   C3: Either one of C1 and C2, which is earlier        The control unit 120 can have an internal timer in order to        determine the termination conditions C1 and C3.

In this embodiment, when determining the conditions C2 and C3 in thetemperature rise section, the control unit 120 can regard that thetemperature index has arrived at the target value in a case in which thetemperature index becomes larger than a control threshold R_(TGT)′(=β·R_(TGT)) equal to the product of the target value R_(TGT) and acoefficient β (β is a positive number slightly smaller than 1. Forexample, β=0.9975) representing an allowable deviation. By thus usingthe arrival at a certain ratio of the target value, instead of thetarget value itself, as the termination condition of a section,temperature control can appropriately be advanced to the next sectioneven in a situation in which the residual deviation from the targetvalue is not completely zero. The control unit 120 can also count thenumber (N_(COUNT)) of measurement periods 20 in which the temperatureindex exceeds the target value R_(TGT) or the control thresholdR_(TGT)′, and regard that the temperature index has reached the targetvalue if the counter N_(COUNT) becomes equal to a determinationthreshold M (M is an integer larger than 1. For example, M=3). By thususing the condition that the temperature index has reached the thresholdvalue a plurality of times as the termination condition of the section,it is possible to reduce the possibility that temperature controladvances to the next section at a very early timing as a result oferroneous determination caused by an error of resistance valuemeasurement. This is useful to implement robust condition determinationin a situation in which the measurement circuit 150 may undergo aninfluence of noise (for example, an instantaneous current valuevariation).

In the next clause, a more specific configuration example of the heatingprofile 50 will be explained in order for individual sections.

<<2. Configuration Example of Heating Profile>>

<2-1. Initial Temperature Rise (S0)>

The section S0 is a section at the beginning of the heating profile 50.“Section type” of the section S0 is “PID control section”, and “Targettemperature” is the first temperature H1. “Target temperature resistancevalue” is a resistance value (to be referred to as R1 hereinafter)corresponding to the first temperature H1. “PID control type” of thesection S0 can be “constant”, and the time required to raise thetemperature can be shortened as much as possible by setting theproportional gain K p of “Gains” at a value higher than those of othersections. “Termination condition” of the section S0 is the condition C2,more specifically, the arrival of the first temperature index at theresistance value R1.

The control unit 120 may further divide the section S0 into a first-halfsection and a second-half section, and, in the first-half section, cansupply electric power from the battery 140 to the heating unit 130 at amaximum settable duty ratio regardless of the gain value and thetemperature index value. This can efficiently shorten the preheatingperiod, and rapidly start delivery of aerosol to the user.

<2-2. Temperature-Maintaining During Preheating (S1)>

“Section type” of the section 51 is “PID control section”, and “Targettemperature” is the first temperature H1. “Target temperature resistancevalue” is the resistance value R1 corresponding to the first temperatureH1. “PID control type” of the section S1 can be “constant”. “Gains” ofthe section S1 can be set at a value that stabilizes the temperature ofthe heating unit 130 near the first temperature H1 (for example, aproportional gain having a value smaller than that of the proportionalgain designated for the section S0 may be set for the section S1),unlike the case of the section S0 in which the temperature is rapidlyraised. “Time length” of the section S1 can be set at a value within therange of, for example, a few seconds. “Termination condition” of thesection S1 is the condition C1, more specifically, the elapse of timeindicated by “Time length”. The control unit 120 sets the timer at thestart of the section S1, and notifies the user of the end of thepreheating period if the control unit 120 determines that the timeindicated by “Time length” has elapsed. This notification can beperformed by one or both of light emission of the light emitting unit125 by a predetermined light emission pattern and the vibration of thevibration unit 126 by a predetermined vibration pattern. Upon sensingthis notification, the user recognizes that preparations of inhalationare complete and inhalation can be started.

<2-3. Session Start (S2)>

“Session type” of the section S2 is “PID control section”, and “targettemperature” is the first temperature H1. “Target temperature resistancevalue” is the resistance value R1 corresponding to the first temperatureH1. “PID control type” of the section S2 can be “constant”. “Gains” ofthe section S2 can be the same as that of the section S1. “Time length”of the section S2 can be set at a value within the range of, forexample, a few seconds to about ten seconds. “Termination condition” ofthe section S2 is the condition C1, more specifically, the elapse oftime indicated by “Time length”. If the control unit 120 determines thatthe time indicated by “Time length” has elapsed, the control unit 120terminates the section S2 and cause temperature control to transition tothe section S3.

The user normally starts inhaling aerosol generated by the aerosolgenerating device 10 from the section S2. The control unit 120 canmeasure one or more of: the number of times of inhalation, the frequencyof inhalation, the inhalation time of each inhalation, and thecumulative inhalation time, based on an inhalation detection signalinput from the inhalation detection unit 124, and can store themeasurement results in the storage unit 121. This measurement can alsobe performed continuously from the section S3 as well.

<2-4. Temperature Fall (S3)>

“Section type” of the section S3 is “OFF section”, and “Targettemperature” is the second temperature H2. “Target temperatureresistance value” is a resistance value (to be referred to as R2hereinafter) corresponding to the second temperature H2. That is, in thesection S3, the control unit 120 stops causing electric power to besupplied from the battery 140 to the heating unit 130 so that thetemperature of the heating unit 130 falls to the second temperature H2lower than the first temperature H1. Since the section S3 is an OFFsection, “PID control type” and “Gains” are not set. “Time length” ofthe section S3 can be set at a value within the range of, for example,tens of seconds. “Termination condition” of the section S3 is thecondition C3. More specifically, the control unit 120 terminates thesection S3 when it is determined from the second temperature index basedon the output value from the thermistor 155 that the temperature of theheating unit 130 has reached the second temperature H2. However, evenbefore the temperature of the heating unit 130 reaches the secondtemperature H2, the control unit 120 terminates the section S3 when thetime indicated by “Time length” has elapsed from the start of thesection S3. In other words, the control unit 120 terminates the sectionS3 based on an earlier one of the arrival of the second temperatureindex at the target value and the elapse of the predetermined time fromthe start of the section, and causes temperature control to transitionto the section S4.

Note that when the section S3 is terminated by the arrival of the secondtemperature index at the target value earlier than a time (for example,T4 shown in FIG. 7 ) at which the time indicated by “Time length”elapses from the start of the section S3, the total time of the sessionshortens if the time length of the succeeding section does not change.An early termination of the session frustrates the user or brings theinconvenience that the aerosol source included in the aerosol generatingsubstrate is not sufficiently used up. Therefore, when terminating thesection S3 earlier than a time point at which the time indicated by“Time length” of the section S3 elapses, the control unit 120 adds theresidual time before that time point to “Time length” designated for thesucceeding section (for example, the section S4). FIG. 8 shows atemperature profile 40 a of a case where the remaining time is added tothe time length of the subsequent section S4 because the termination ofthe section S3 is earlier than the predetermined time, in comparisonwith the temperature profile 40 shown in FIG. 7 . In the temperatureprofile 40 a, the temperature of the heating unit 130 reaches the secondtemperature H2 at T3 a before T4. As a consequence, the residual time(T4-T3 a) is added to the time length of the section S4. In an OFFsection such as the section S3, the fall rate of the temperature of theheating unit 130 changes depending on the environmental conditions.Accordingly, the use of the method of compensating for the time lengthof a session as described above is useful to effectively consume theaerosol source and improve the satisfaction of the user.

<2-5. Correction of Second Temperature Index>

As described above, the second temperature index based on the outputvalue from the thermistor 155 follows the change in temperature of theheating unit 130 with a certain delay. Therefore, if the control unit120 directly compares the second temperature index with the target valuein order to determine termination of the section S3, the temperature ofthe heating unit 130 may have further dropped from the targettemperature at the end of the section S3. If the temperature of theheating unit 130 is too low, the amount of aerosol generated from theaerosol generating substrate reduces, and the tobacco flavor decreases.In this embodiment, therefore, in the section S3, the control unit 120corrects the second temperature index so as to compensate for the delayof change of the second temperature index, and compares the correctedindex value with the target value, thereby determining whether thetemperature of the heating unit 130 has reached the second temperatureH2. To correct the second temperature index, the control unit 120 uses apredetermined relationship between the first temperature index and thesecond temperature index. For example, in a section (for example, thesection S0) preceding the section S3, the control unit 120 acquires thesecond temperature index based on the output value from the thermistor155, in addition to the first temperature index based on the electricalresistance value of the heating unit 130. Then, prior to the start ofthe section S3, the control unit 120 determines the relationship betweenthe acquired first and second temperature indices.

FIG. 9 is an explanatory diagram for explaining the relationship betweenthe first and second temperature indices. A solid-line graph 61represents an example of a temporal change of the value of the firsttemperature index when temperature control is performed till T4 inaccordance with the heating profile 50 explained with reference to FIG.7 . A graph 62 of an alternate long and short dash line represents anexample of a temporal change of the value of the second temperatureindex when temperature control is performed till T4 in accordance withthe same heating profile 50. As can be understood from the comparison ofthe two graphs 61 and 62, the first temperature index and the secondtemperature index are almost linear loci especially in the beginning(for example, the section S0) of the preheating period, but atemperature change rate (a gradient g₂ in the drawing) indicated by thesecond temperature index is relatively smaller than a temperature changerate (a gradient g₁ in the drawing), so even after the first temperatureindex has reached the target value at T1, the second temperature indexhas not reached the target value. The difference between the secondtemperature index and the target value gradually decreases from thesection 51 to the section S2 (because heat of the heating unit 130 isconducted to the thermistor 155 via the heat insulating member 108), buta difference d₁ from the target value still remains even at T3. When thesection S3, that is, an OFF section starts at T3, the first temperatureindex and the second temperature index draw substantially linear graphsagain while falling.

Assume, as a simple model, that the gradient difference between the twotemperature indices when the temperature of the heating unit 130 dropsis equal to the gradient difference (g₁−g₂) between the two temperatureindices when the temperature rises (however, the sign is inverted).Then, the control unit 120 can calculate a correction value to beapplied to the second temperature index in the section S3, based on thetemperature difference d₁ indicated by the two indices at the startingpoint in time of the section S3 and the difference (g₁−g₂) between thetemperature change rate acquired in the section S0. To simplify theexplanation, assume that the temperature value is used to determine thetermination condition of the section S3 instead of the resistance value.In this case, a correction value Δh(t) to be added to the value of thesecond temperature index at the point in time when a time t has elapsedfrom the start of the section S3 can be calculated as indicated by anequation below:

Δh(t)=d ₁−(g ₁ −g ₂)·t  (3)

Note that instead of individually acquiring the gradient g₁ of the firsttemperature index and the gradient g₂ of the second temperature index,the control unit 120 can acquire, for example, the difference (g₁−g₂)between the two gradients by dividing the difference (d₂ in FIG. 9 )between the index values at the point in time at which the value of thesecond temperature index reaches the value corresponding to the secondtemperature H2 by the time elapsed until that point in time.

The above-described relationship between the first temperature index andthe second temperature index can also be acquired and stored in thestorage unit 121 before heating is started, not in the sections S0 to S2immediately before the section S3. As the first example, therelationship between the first temperature index and the secondtemperature index can be acquired in an evaluation test before theaerosol generating device 10 is shipped. As the second example, thecontrol unit 120 can acquire and record the values of the first andsecond temperature indices at the start and end of the section S3 ineach session. In this case, to determine the termination condition ofthe section S3 in a new session, the control unit 120 can calculate theabove-described correction value Δh(t) of the second temperature indexbased on the difference between the change rates of two temperatureindex values already recorded in the past, and use the calculationresult. As a derivation of the second example, the two temperature indexvalues can also be recorded in relation to the environmental temperaturemeasured by a temperature sensor, and the control unit 120 may alsocalculate the correction value of the second temperature index based onthe record corresponding to the environmental temperature at the pointin time of a new session. The aerosol generating device 10 may have atemperature sensor for measuring the environmental temperature, orreceive environmental temperature data from another device via thewireless I/F 127 or the connection I/F 128.

As described above, the control unit 120 can avoid the temperature ofthe heating unit 130 from excessively falling from the secondtemperature H2 in the section S3 and prevent a decrease in tobaccoflavor, by using the index value so corrected as to compensate for thedelay of change of the second temperature index in order to determinethe termination condition.

<2-6. Temperature-Maintaining after Temperature Fall (S4)>

“Section type” of the section S4 is “PID control section”. That is, thecontrol unit 120 restarts the supply of electric power from the battery140 to the heating unit 130 in response to the transition of temperaturecontrol from the section S3 to the section S4. “Target temperature” ofthe section S4 is the second temperature H2. “Target temperatureresistance value” is the resistance value R2 corresponding to the secondtemperature H2. “PID control type” of the section S4 can be “constant”.“Gains” of the section S4 can be the same as that set in the section 51and the section S2. “Time length” of the section S4 can be set to, forexample, tens of seconds to a few minutes. “Termination condition” ofthe section S4 is the condition C1, more specifically, the elapse oftime indicated by “time length”. If the control unit 120 determines thatthe time indicated by “Time length” has elapsed, the control unit 120terminates the section S4 and causes temperature control to transitionto the section S5.

When the section S3 is terminated because the time indicated by “Timelength” of the section S3 has elapsed, there is a possibility that thetemperature of the heating unit 130 at the terminating point in time issignificantly higher than the second temperature H2. Meanwhile, “Gains”of the section S4 has values tuned for the purpose of maintaining thetemperature constant. Therefore, if PID control is resumed by settingthe target temperature at the second temperature H2 in the section S4,the temperature of the heating unit 130 may behave unstably due to thedivergence of the temperature at the start of the section S4 from thesecond temperature H2. Therefore, if the temperature of the heating unit130 at the terminating point in time of the section S3 is higher thanthe second temperature H2, the control unit 120 can handle thetemperature at that point in time as the target temperature of thesection S4. That is, the control unit 120 can reset the targettemperature resistance value corresponding to the temperature at theterminating point in time of the section S3 as the target value of PIDcontrol in the section S4. This can stabilize the temperature of theheating unit 130 in the section S4. FIG. 10 shows two examples(temperature profiles 41 a and 41 b) of the temperature profile in acase where the target value of PID control in the section S4 is reset tothe target temperature resistance value corresponding to the temperatureat the terminating point in time of the section S3, in comparison withthe temperature profile 40 shown in FIG. 7 . The temperature profile 41a is an example in a case where a temperature H2 a at the terminatingpoint in time of the section S3 is lower than the third temperature H3.The temperature profile 41 b is an example in a case where a temperatureH2 b at the terminating point in time of the section S3 is higher thanthe third temperature H3.

Though an example in which “Termination condition” of the section S3 isthe condition C3 has been explained above, “Termination condition” ofthe section S3 may be the condition C2 as the first modification. Inthis case, the control unit 120 maintains temperature control in thesection S3 until the temperature indicated by the second temperatureindex reaches the second temperature H2, regardless of the time elapsedfrom the start of the section S3. This can avoid the situation in whichthe temperature of the heating unit 130 diverges from the secondtemperature H2 when the section S4 starts. In this modification, if thetemperature of the heating unit 130 reaches the target temperature H2later than the time point (for example, T4 in FIG. 7 ) at which “Timelength” of the section S3 elapses from the start of the section S3, thecontrol unit 120 may subtract, from “time length” of the section S4, theovertime with respect to that time point (that is, the section S4 may beshortened). This can avoid the time length of the whole heating periodfrom excessively prolonging, and prevent a decrease in tobacco flavorcaused by depletion of the aerosol source. FIG. 11 shows a temperatureprofile 42 in a case where the section S4 is shortened as a result ofprolongation of the section S3 in the first modification, in comparisonwith the temperature profile 40 shown in FIG. 7 . In the temperatureprofile 42, the temperature of the heating unit 130 reaches the secondtemperature H2 at T4 a after T4. Consequently, the time length of thesection S4 is reduced by the overtime (T4 a-T4).

As the second modification, “Termination condition” of the section S3 isthe condition C2, but the control unit 120 may reset the targettemperature of the section S3 from the second temperature H2 to thethird temperature H3 at a point in time when the time indicated by “Timelength” of the section S3 has elapsed. If the temperature of the heatingunit 130 reaches the target temperature H3 later than the time point(for example, T4 in FIG. 7 ) at which “time length” of the section S3elapses, the control unit 120 may subtract, from “time length” of thesection S4, the overtime with respect to that time point (that is, thesection S4 may be shortened), in this modification as well. This canavoid the time length of the whole heating period from excessivelyprolonging. FIG. 12 shows a temperature profile 43 in a case where thesection S4 is shortened as a result of prolongation of the section S3 inthe second modification, in comparison with the temperature profile 40shown in FIG. 7 . In the temperature profile 43, the target temperatureis reset to the third temperature H3 at T4, and the temperature of theheating unit 130 reaches the third temperature H3 at T4 b. Consequently,the time length of the section S4 is reduced by the overtime (T4 b-T4).

<2-7. Temperature Rerise (S5)>

“Section type” of the section S5 is “PID control section”. “Targettemperature” of the section S5 is the third temperature H3. “Targettemperature resistance value” is a resistance value (to be referred toas R3 hereinafter) corresponding to the third temperature H3. “PIDcontrol type” of the section S5 is “linear interpolation”. That is, thecontrol unit 120 raises the target value of PID control step by stepfrom the target value (for example, the resistance value R2) of thesection S4 to the resistance value R3 from the start to the end of thissection. “Gains” of the section S5 can be either the same as ordifferent from that set in the section S4. “Time length” of the sectionS5 can be set to, for example, tens of seconds to a few minutes.“Termination condition” of the section S5 is the condition C1. Morespecifically, when the time indicated by “Time length” has elapsed fromthe start of the section S5, the control unit 120 terminates the sectionS5 and causes temperature control to transition to the section S6.

Note that if “Termination condition” of the section S3 is the conditionC2 as in the first modification explained in relation to the section S4,there is a possibility that the overtime to be subtracted becomes largerthan “Time length” predefined for the section S4 as a result of a largedelay of the termination of the section S3. In this modification,therefore, if the temperature of the heating unit 130 has reached thetarget temperature H2 later than the time point (for example, T5 in FIG.7 ) at which the total time of “time length” of the section S3 and “timelength” of the section S4 has elapsed from the start of the section S3,the control unit 120 may subtract, from “Time length” of the section S5,the overtime with respect to that time point (that is, the section S5may be shortened). In this case, the section S4 is skipped. FIG. 13shows a temperature profile 44 in a case where the section S4 is skippedand the section S5 is shortened as a result of prolongation of thesection S3 in the first modification, in comparison with the temperatureprofile 40 shown in FIG. 7 . In the temperature profile 44, thetemperature of the heating unit 130 reaches the second temperature H2 atT5 a after T5. Consequently, the time length of the section S5 isreduced by the overtime (T5 a-T5).

The method of shortening the section S5 shown in FIG. 13 can also becombined with the second modification explained in relation to thesection S4. FIG. 14 shows a temperature profile 45 in a case where thesection S4 is skipped and the section S5 is shortened as a result ofprolongation of the section S3, in comparison with the temperatureprofile 40 shown in FIG. 7 . In the temperature profile 45, thetemperature of the heating unit 130 reaches the third temperature H3(the reset target temperature) at T5 b after T5. Consequently, the timelength of the section S5 is reduced by the overtime (T5 b-T5).

<2-8. Temperature-Maintaining after Temperature Rerise (S6)>

“Section type” of the section S6 is “PID control section”. “Targettemperature” of the section S6 is the third temperature H3. “Targettemperature resistance value” is the resistance value R3 correspondingto the third temperature H3. “PID control type” of the section S6 can be“constant”. “Gains” of the section S6 can be the same as those set inthe section S1, the section S2, and the section S4. “Time length” of thesection S6 can be set at a value within the range of, for example, tensof seconds. “Termination condition” of the section S6 is the conditionC1, more specifically, the elapse of time indicated by “Time length”. Ifthe control unit 120 determines that the time indicated by “Time length”has elapsed, the control unit 120 terminates the section S6 and causestemperature control to transition to the section S7.

Like the section S4, “Gains” of the section S6 has values tuned for thepurpose of maintaining the temperature constant. Although the targettemperature of the section S6 is the third temperature H3, if PIDcontrol is resumed by setting the target value of the section S6 at theresistance value R3 when the temperature at the start of the section S6significantly diverges from the third temperature H3, the temperature ofthe heating unit 130 may behave unstably. Therefore, if the temperatureof the heating unit 130 at a certain reference point in time (forexample, at the starting point in time of the section S6) significantlydiverges from the third temperature H3 (for example, is higher than thethird temperature H3), the control unit 120 may handle the temperatureat that point in time as the target temperature of the section S6. Thatis, the control unit 120 may reset the target value of PID control inthe section S6 to a target temperature resistance value corresponding tothe current temperature at the reference point in time. This canstabilize the temperature of the heating unit 130 in the section S6.FIG. 15 shows a temperature profile 46 in a case where the target valueof PID control in the section S6 is reset to the target temperatureresistance value corresponding to the current temperature at thestarting point in time of the section S6, in comparison with thetemperature profile 40 shown in FIG. 7 . In the temperature profile 46,the target temperature is reset to a current temperature H3 a higherthan the third temperature at T6, and the temperature of the heatingunit 130 is maintained at the temperature H3 a throughout the sectionS6.

<2-9. Termination (S7)>

“Section type” of the section S7 is “OFF section”. In the section S7,the temperature of the heating unit 130 falls toward the environmentaltemperature H0. “Target temperature”, “Target temperature resistancevalue”, and “Gains” of the section S7 need not be set. “Time length” ofthe section S7 can be set at a value within the range of, for example, afew seconds to tens of seconds. “Termination condition” of the sectionS7 is the condition C1, more specifically, the elapse of time indicatedby “Time length”. If the control unit 120 determines that the timeindicated by “Time length” has elapsed, the control unit 120 terminatesthe heating period. At the start of the section S7, the control unit 120can notify the user of an approach of the end of the inhalable period,by the light emission of the light emitting unit 125 or the vibration ofthe vibration unit 126. The control unit 120 can also notify the user ofthe end of the inhalable period at the end of the section S7, by thelight emission of the light emitting unit 125 or the vibration of thevibration unit 126.

<2-10. Recovery (S4 a)/Maintaining (S4 b) after Excessive TemperatureFall>

An example has been described above where, when the second temperatureindex has reached the resistance value R2 corresponding to the secondtemperature H2, the section S3 is terminated and temperature control iscaused to transition to the section S4. In this case, if correction ofthe second temperature index is performed with high accuracy, thetemperature of the heating unit 130 is substantially equal to the secondtemperature H2 at the time of transition to the section S4. In practice,however, the corrected second temperature index contains an error tosome extent, so the temperature of the heating unit 130 maysignificantly diverge from the second temperature H2 (for example, thetemperature has fallen to a lower temperature) at the time oftransitioning to the section S4. As a third modification, therefore, thecontrol unit 120 may acquire a first temperature index when starting thesection S4, and, in the section S4, control the supply of electric powerfrom the battery 140 to the heating unit 130 by using a controlparameter set that differs in accordance with the temperature of theheating unit 130 indicated by the acquired first temperature index.

Let H2 _(C) be the temperature of the heating unit 130 indicated by thefirst temperature index when starting the section S4. In this thirdmodification, if the temperature H2 _(C) is lower than the secondtemperature H2 (H2 _(C)<H2), the control unit 120 uses a first controlparameter set for recovering (raising) the temperature of the heatingunit 130 to the second temperature H2. On the other hand, if thetemperature H2 _(C) is equal to or higher than the second temperature H2(H2 _(C)≥H2), the control unit 120 uses a second control parameter setfor maintaining the temperature of the heating unit 130 at thetemperature H2 _(C). For example, the first control parameter setincludes a value K_(p1) of the proportional gain of feedback control,the second control parameter set includes K_(p2) of the proportionalgain of feedback control, and K_(p1) is larger than K_(p2). In addition,the values of one or both of the integral gain and the differential gaincan be different between the first control parameter set and the secondcontrol parameter set. By thus switching between the control parametersets of feedback control depending on the temperature of the heatingunit 130 at the start of the section S4, it is possible to prevent thetemperature of the heating unit 130 from deviating from a desiredtemperature (for example, the second temperature H2) in the middle ofthe session, and thereby it is possible to mitigate a decrease in thetobacco flavor.

If it is determined that the temperature of the heating unit 130 isrecovered to the second temperature H2 by temperature control using thefirst control parameter set, the control unit 120 may switch the controlparameter set from the first control parameter set to the second controlparameter set. Typically, it is assumed that even when the temperatureof the heating unit 130 excessively drops due to the error in thecorrected second temperature index, the degree of this temperature dropis small. Therefore, the stability of the temperature of the heatingunit 130 in the section S4 can be increased by switching the controlparameter set to the second control parameter set after the temperatureof the heating unit 130 is recovered within a short time.

FIG. 16 shows an example of a temperature profile in a case where thesection S4 includes a recovery section in the third modification. Inthis example shown in FIG. 16 , the temperature H2 _(C) when the sectionS4 is started is lower than the second temperature H2. Therefore, thecontrol unit 120 sets a recovery section S4 a at the beginning of thesection S4, and performs PID control by using the first controlparameter set including the value K_(p1) of a larger proportional gain.The target value of this PID control can be the resistance value R2corresponding to the second temperature H2. This PID control brings thetemperature of the heating unit 130 back to the second temperature H2 atT4 c. Then, the control unit 120 causes temperature control totransition from the recovery section S4 a to a maintaining section S4 b,and switches the control parameter set for PID control to the secondcontrol parameter set including the value K_(p2) of the proportionalgain. Consequently, the temperature of the heating unit 130 ismaintained near the second temperature H2 until T5.

Note that when determining whether the first temperature index hasreached the target value R2 in the recovery section S4 a, the controlunit 120 may perform threshold determination taking account of theabove-described coefficient β representing the allowable deviation.Moreover, a condition that the first temperature index reached thethreshold value M times may be used as the condition to terminate therecovery section S4 a (that is, transition to the maintain section S4b).

The first control parameter set for use in the recovery section S4 a maybe the same as the control parameter set used to initially raise thetemperature of the heating unit 130 in the section S0. For example, thevalue K_(p1) of the proportional gain of the first control parameter setmay be equal to the value of the proportional gain used when initiallyraising the temperature. By thus reusing the control parameter setbetween sections having a similar control purpose (for example, a rapidtemperature rise, a moderate temperature rise, or temperaturemaintaining), it is possible to avoid increasing the size of profiledata describing the heating profile, and save the memory resource forstoring the data (and the communication resource for communicating thedata).

<2-11. Configuration Example of Profile Data>

It is useful to define a structuralized standard data format capable ofdescribing the operational specification of each section of the heatingprofile 50 explained so far. The standard data format makes it easy toswitch between the heating profiles 50 and change behavior oftemperature control, in various scenes such as upgrading the operationalspecification, a change of the type of a tobacco article, and selectionof a temperature profile that matches a user preference. Severalexamples of the configuration of the profile data 51 describing theheating profile 50 will be explained below.

FIG. 17A is an explanatory diagram for explaining the first example ofthe configuration of the profile data 51. Referring to FIG. 17A, theprofile data 51 contains seven information elements, that is, SectionNumber 52, Control Method 53, Target Temperature 54, Target TemperatureResistance Value 55, Gains 56, Time Length 57, and Termination Condition58.

Section Number 52 is a number (identifier) for identifying each section.Control Method 53 is an information element for designating a controlmethod to be applied to temperature control of each section from aplurality of control methods. In this example, the control method 53 isequivalent to a combination of the above-described control parameters“Section type” and “PID control type”, and can take one of values “0”,“1”, and “2”. In the example shown in FIG. 17A, Control Method 53 of asection S_(n) indicates the value “1”, and this value represents thatthe control method to be applied to this section is PID control and thecontrol target value must be maintained constant in the section. ControlMethod 53 of a section S_(n+1) indicates the value “0”, and this valuerepresents that the control method to be applied to this section isstopping power supply to the heating unit 130. That is, the sectionS_(n+1) in this example is an OFF section. Control Method 53 of asection S_(n+2) indicates the value “2”, and this value represents thecontrol method to be applied to this section is PID control and thecontrol target value must be changed linearly in this section.

Target Temperature 54 and Target Temperature Resistance Value 55 areinformation elements for respectively designating the control parameters“Target temperature” and “Target temperature resistance value”. Notethat when temperature control is performed by using the temperatureitself as a controlled variable, Target Temperature Resistance Value 55may be omitted from the profile data 51. Gains 56 is an informationelement for designating the above-described control parameter set“Gains”. Gains 56 can be blank for an OFF section. Time Length 57 andTermination Condition 58 are information elements for respectivelydesignating the above-described control parameters “Time length” and“Termination condition”.

FIG. 17B is an explanatory diagram showing the second example of theconfiguration of the profile data 51. Referring to FIG. 17B, the profiledata 51 contains a common area 51 a and a sectional area 51 b.

The common area 51 a is a data area for describing information that iscommon over a plurality of sections. In this example shown in FIG. 17B,the common area 51 a includes three information elements 59 a, 59 b, and59 c. The information element 59 a designates a number (identifier) foruniquely identifying a control profile to be described by this profiledata. The information element 59 b designates a first gain set K₁, andthe information element 59 c designates a second gain set K₂. The gainset K₁ contains a proportional gain value K_(p1), an integral gain valueK_(i1), and a differential gain value K_(d1), and the gain set K₂contains a proportional gain value K_(p2), an integral gain valueK_(i2), and a differential gain value K_(d2).

The sectional area 51 b is a data area for describing information uniqueto each section. In the example shown in FIG. 17B, the sectional area 51b contains six information elements, that is, Section Number 52, TargetTemperature 54, Target Temperature Resistance Value 55, Gains 56, TimeLength 57, and Termination Condition 58. In this example, Control Method53 shown in FIG. 17A is omitted. Instead, if the value of TargetTemperature 54 indicates a value larger than 0, this value representsthat the PID control method must be applied to the section. In addition,if the value of Target Temperature 54 indicates 0, this value representsthat the section is an OFF section. In the example shown in FIG. 17B,Target Temperature 54 indicates 0 for the section S_(n+1), so thesection S_(n+1) is an OFF section. In this manner, by assigning meaningsof two or more control parameters to a single information element in theprofile data 51, the number of information elements of the profile data51 can be reduced. Furthermore, Gains 56 designates one of the gain setK₁ and the gain set K₂, instead of specific values of the three types ofgains as shown in the example of FIG. 17A. For example, the gain set K₁is designated for the section S_(n), and the gain set K₂ is designatedfor the section S_(n+2) and a section S_(n+3). In this manner, byenabling, in the sectional area 51 b, to designate one of the limitednumber of choices defined in the common area 51 a, repetitions ofredundant value definition can be avoided and data size of the profiledata 51 can be reduced. Not only the gains but also another controlparameter such as the temperature or the resistance value may bedesignated by this technique using the common area 51 a.

It is possible to allocate the structuralized standard data format suchas the profile data 51 described above to a predetermined data area ofthe storage unit 121, thereby making data in the data area rewritable.This makes it possible to change behavior of temperature control to beexecuted by the control unit 120 by only rewriting the profile data 51without changing any control program. In this case, all the control unit120 needs to do is reading out the latest contents from the same dataarea of the storage unit 121, and use the readout data.

The configurations of the profile data 51 are not limited to theexamples shown in FIGS. 17A and 17B. The profile data 51 may containadditional information elements, or some of the information elementsshown in the drawings may be omitted. For example, the profile data 51may contain one of the followings as information that is common over aplurality of sections:

-   -   The name of the heating profile    -   The version number of the heating profile    -   The number of sections forming the heating profile    -   A calibration value (that can be written based on the result of        a test before product shipment) to be added to a temperature or        a resistance value, in order to absorb a manufacturing tolerance        of the resistive-temperature characteristic of the heating unit        of each product

Also, the profile data 51 may additionally contain one of the followingsas information that can be designated for each section:

-   -   Whether to determine the duty ratio of power supply to the        heating unit by PID control or to use a maximum duty ratio    -   Whether to reset the cumulative deviation of the integral term        of PID control at the start of a section    -   Types of abnormality to be detected

In this specification, an example has been mainly described where powersupply to the heating unit 130 is stopped and no pulse for measuring thetemperature or the resistance value is applied to the heating unit 130in an OFF section. However, control methods that can be designated bythe profile data 51 may include a method in which power supply (forheating) to the heating unit 130 is stopped but a pulse for measuringthe temperature or the resistance value can be applied to the heatingunit 130. A section for which such a control method is designated mayalso be called “OFF section”. In addition, the profile data 51 may alsodesignate a termination condition other than the conditions C1 to C3described above for each section. For example, the designatabletermination conditions include a condition based on the detected countof inhalation or the detected total time of inhalation.

Some of the control parameters of the heating profile 50 explained inthis clause may be described in a separate storage area instead of beingdescribed in the profile data 51, or may be described by a program codeof a control program.

<<3. Abnormality Detection>>

The control unit 120 monitors whether there is an abnormality in theoperation of the aerosol generating device 10 while performingtemperature control in accordance with the heating profile 50 describedin the profile data 51. When an abnormality is detected, the controlunit 120 stops the supply of electric power from the battery 140 to theheating unit 130, stores an error code indicating the type of thedetected abnormality in the storage unit 121, and notifies the user ofthe occurrence of the abnormality. Several abnormality types detectableby the control unit 120 in relation to temperature control of theheating unit 130 will be explained below.

<<3-1. Trouble of Measurement Circuit>>

If a trouble occurs in the measurement circuit 150 and no accuratetemperature index can be acquired, the control unit 120 cannot recognizethis state even when the temperature of the heating unit 130 becomesexcessively high. To prevent a situation like this, the control unit 120monitors an amount of change in the first temperature index perpredetermined time interval while supplying electric power to theheating unit 130 in the section S0. Then, if the amount of change in thefirst temperature index becomes smaller than a threshold value, thecontrol unit 120 determines that a trouble may have occurred in themeasurement circuit 150, and stops power supply from the battery 140 tothe heating unit 130. In this case, the threshold value can be atemperature change of 10° C. (a change in resistance value equivalent to10° C.) during a time interval of three seconds.

<3-2. Preheating Failure>

If the temperature of the heating unit 130 does not reach the targetvalue (for example, the first temperature H1) even when electric poweris supplied to the heating unit 130 over a sufficient time in thepreheating period, there is a possibility that the power supply routefrom the battery 140 to the heating unit 130 has a trouble or theenvironment has an abnormality, for example, the environmentaltemperature is abnormally low. To detect a situation like this andprevent the waste of electric power, if the control unit 120 determinesfrom the first temperature index that the temperature of the heatingunit 130 has not reached the target temperature at a point in time whena predetermined time has elapsed from the start of heating in thesection S0, the control unit 120 stops power supply from the battery 140to the heating unit 130. The predetermined time herein may be equal tothe time length designated for the section S0 by the heating profile 50(or may be defined independently of the heating profile 50), and may be,for example, 60 seconds.

<3-3. Overheating (When Heating Is Resumed)>

As described previously, the second temperature index based on theoutput value from the thermistor 155 has a delay or an error to someextent. Therefore, determining from the first temperature index whetherthe temperature of the heating unit 130 is excessively high at thetermination point in time of the section S3 as an OFF section canfurther improve safety of the device. More specifically, when the timelength designated by the heating profile 50 has elapsed from the startof the section S3 (before transitioning to the section S4), the controlunit 120 compares the temperature of the heating unit 130 indicated bythe first temperature index with the first temperature H1. Then, if thetemperature of the heating unit 130 is found to be higher than the firsttemperature H1, the control unit 120 determines that the heating unit130 is overheating, and terminates the temperature control conforming tothe heating profile 50. Note that the detection of overheating based onthe first temperature index may be performed not only when heating isresumed but also periodically in sections other than an OFF section.

<3-4. Overheating (OFF Section)>

To make the overheating state of the heating unit 130 detectable even inan OFF state, the control unit 120 may compare the temperature of theheating unit 130 indicated by the second temperature index with thefirst temperature H1 in the section S3. If the temperature of theheating unit 130 is found to be higher than the first temperature H1,the control unit 120 determines that the heating unit 130 isoverheating, and terminates the temperature control conforming to theheating profile 50. This can increase the possibility to detect anoverheating state caused by a certain trouble during an OFF periodearly.

<<4. Process Flow>>

In this clause, flows of main portions of the control process to beexecuted by the control unit 120 of the aerosol generating device 10described above will be explained by using several flowcharts. In thefollowing explanation, a processing step will be abbreviated as S(step).

Note that for the sake of descriptive simplicity, each flowchart doesnot show processing steps for abnormality detection explained in theprevious clause. Abnormality detection may periodically be performed ina part of a normal control routine of the control unit 120, and may alsobe performed at a specific timing, for example, the start of heating ora transition between sections. Alternatively, a detection circuitdifferent from the control unit 120 may detect an abnormality and notifythe control unit 120 of the detected abnormality (by an interrupt signalor the like).

<4-1. Aerosol Generation Process>

FIG. 18 is a flowchart showing an example of the overall flow of anaerosol generation process according to an embodiment.

First, in S101, the control unit 120 monitors an input signal from theinput detection unit 122, and waits for a user input (for example, longpress of a button) requesting the start of heating. If a user inputrequesting the start of heating is detected, the process advances toS103.

In S103, the control unit 120 checks the state of the aerosol generatingdevice 10 in order to start heating. This state check can includecertain check conditions such as whether the residual power amount ofthe battery 140 is sufficient, and whether the front panel 102 has notfallen off. If one or more check conditions are not met, heating is notstarted, and the process returns to S101. If all the check conditionsare met, the process advances to S105.

In S105, the control unit 120 reads out the profile data 51 from apredetermined storage area of the storage unit 121. S107 to S133 afterthat are repeated for each of a plurality of sections included in theheating profile 50 described in the profile data 51.

In S107, the control unit 120 determines whether the current section isa PID control section or an OFF section based on “Section type”designating a control method to be applied to the current section. Ifthe current section is a PID control section, the process advances toS110. On the other hand, if the current section is an OFF section, theprocess advances to S120.

In S110, the control unit 120 executes a temperature control process fora PID control section so that the temperature of the heating unit 130becomes a temperature designated for the current section. A morespecific flow of the temperature control process to be executed in thisstep will be explained later.

In S120, the control unit 120 executes a temperature control process foran OFF section so that the temperature of the heating unit 130 drops tothe temperature designated for the current section. A more specific flowof the temperature control process to be executed in this step will beexplained later.

When the temperature control process in S110 or S120 is terminatedbecause the termination condition is met, the control unit 120determines in S131 whether the heating profile 50 has the next section.If the heating profile 50 has the next section, temperature controltransitions to the next section in S131, and S107 to S133 describedabove are repeated for the next section set as the current section. Ifthere is no next section, the aerosol generation process shown in FIG.18 ends.

<4-2. Temperature Control Process in PID Control Section>

FIG. 19 is a flowchart showing an example of the flow of the temperaturecontrol process for a PID control section, which is executed in S110 ofFIG. 18 .

First, in S111, the control unit 120 acquires the target temperature andthe time length designated for the current section by the heatingprofile 50, and sets the termination condition of the current section.For example, if the termination condition is the condition C1 or C3, thecontrol unit 120 sets the designated time length in a timer andactivates the timer. If the termination condition is the condition C2 orC3, the control unit 120 sets a control threshold (for example, athreshold taking account of an allowable deviation) to be compared withthe first temperature index, based on the designated target temperature.

Then, in S112, the control unit 120 sets PID control parameters of thecurrent section. For example, the control unit 120 sets the targettemperature resistance value as the target value of PID control, theproportional gain, the integral gain, and the differential gain at thevalues designated for the current section by the heating profile 50.

S113 to S118 after that are repeated for each control cycle. First, inS113, the control unit 120 determines whether to linearly interpolatethe target value of PID control. If “linear interpolation” is designatedas “PID control type” of the heating profile 50 for the current section,the control unit 120 resets the target value of PID control by linearinterpolation in S114 such that they change step by step for eachcontrol cycle. If “constant” is set as “PID control type” for thecurrent section, S114 is skipped.

In S115, the control unit 120 acquires the first temperature index basedon the electrical resistance value of the heating unit 130 by using themeasurement circuit 150. This index value acquired in this step can be,for example, an average value as a result of a plurality of times ofresistance value measurement as explained with reference to FIG. 5 .

In S116, the control unit 120 determines whether the terminationcondition of the current section set in S111 is met. If it is determinedthat the termination condition of the current section is not met, theprocess advances to S117.

In S117, the control unit 120 calculates the duty ratio of PWM for thelatest control cycle in accordance with the PID control equationexplained by using equation (1). Then, in S118, the control unit 120outputs control pulses having a pulse width based on the calculated dutyratio to the first switch 131 and the second switch 132, thereby causingelectric power to be supplied from the battery 140 to the heating unit130.

After one control cycle is thus completed, the process advances to thenext control cycle, and S113 to S118 described above are repeated. If itis determined in S116 that the termination condition of the currentsection is met, the temperature control process shown in FIG. 19 isterminated.

<4-3. Temperature Control Process in OFF Section>

(1) First Example

FIG. 20A is a flowchart showing the first example of the flow of thetemperature control process for an OFF section, which is executed inS120 of FIG. 18 .

First, in S121, the control unit 120 acquires the target temperature andthe time length designated for the current section by the heatingprofile 50, and sets the termination condition of the current section.The same examples for setting respective termination conditions asexplained in relation to S111 of FIG. 19 may be applied here.

Then, in S122, the control unit 120 acquires the second temperatureindex based on the output value from the thermistor 155. Then, in S123,the control unit 120 corrects the value of the second temperature indexacquired in S122 by using the previously determined relationship betweenthe first temperature index and the second temperature index, so as tocompensate for a delay of a change in value.

In S124, the control unit 120 determines whether the terminationcondition of the current section set in S121 is met, based on the valueof the second temperature index corrected in S123. If it is determinedthat the termination condition of the current section is not met, theprocess returns to S122, and S122 to S124 described above are repeated.If it is determined that the termination condition of the currentsection is met, the temperature control process shown in FIG. 20A isterminated.

(2) Second Example

FIG. 20B is a flowchart showing the second example of the flow of thetemperature control process for an OFF period, which is executed in S120of FIG. 18 .

S121 to S124 shown in FIG. 20B can be the same processing steps as S121to S124 shown in FIG. 20A, so explanations thereof will be omitted.

If it is determined in S124 that the termination condition of thecurrent section is met, the control unit 120 determines in S125 whetherthe current section ends earlier than a predetermined time. Thepredetermined time herein is the time point at which the time lengthacquired in S121 elapses from the start time of the current section. Ifthe current section ends earlier than the predetermined time, thecontrol unit 120 adds, in S126, a residual time until the predeterminedtime to the time length designated by the heating profile 50 for thesubsequent section of the current section.

If it is determined in S125 that the current section does not endearlier than the predetermined time (ends at the predetermined time),the time length of the subsequent section is not changed, and thetemperature control process shown in FIG. 20B is terminated.

(3) Third Example

FIG. 20C is a flowchart showing the third example of the flow of thetemperature control process for an OFF section, which is executed inS120 of FIG. 18 .

S121 to S126 shown in FIG. 20C can be the same as S121 to S126 shown inFIG. 20B except that the process advances to S127 if it is determined inS125 that the current section does not end earlier than thepredetermined time, so explanations thereof will be omitted.

In S127, the control unit 120 determines whether the current sectionends later than a predetermined time. If the current section ends laterthan the predetermined time, the control unit 120 subtracts, in S128, anovertime with respect to the predetermined time from the time lengthdesignated by the heating profile 50 for the subsequent section of thecurrent section.

If it is determined in S127 that the current section does not end laterthan the predetermined time (ends at the predetermined time), the timelength of the subsequent section is not changed, and the temperaturecontrol process shown in FIG. 20C is terminated.

Note that in S128, if the time length designated for the subsequentsection by the heating profile 50 is shorter than the overtime from thepredetermined time, the control unit 120 may skip temperature control ofthe subsequent section, and perform time subtraction from the timelength designated for the further next section.

<4-4. Termination Determination Process (Section S0)>

FIG. 21 is a flowchart showing an example of the flow of a terminationdetermination process corresponding to S116 in FIG. 19 , which isapplicable to the section S0. Note that in the third modificationdescribed above, this termination determination process shown in FIG. 21may also be applied to the recovery section S4 a.

First, in S141, the control unit 120 acquires a control threshold equalto the product of the target value of temperature control of the currentsection and a coefficient representing an allowable deviation. Note thatthis processing step need only be performed once at the beginning ofeach section.

Then, in S142, the control unit 120 determines whether the index valueof the first temperature index exceeds the control threshold acquired inS141. If the index value of the first temperature index exceeds thedetermination threshold, the process advances to S143. On the otherhand, if the index value of the first temperature index does not exceedthe determination threshold, the process advances to S145.

In S143, the control unit 120 adds 1 to (increments) the counterN_(COUNT) for counting the number of times of threshold fulfillment.Note that the counter N_(COUNT) is initialized to 0 at the beginning ofeach section. Then, in S144, the control unit 120 determines whether thecounter N_(COUNT) has reached the determination threshold M. If thecounter N_(COUNT) has reached the determination threshold M, the processadvances to S146. On the other hand, if the counter N_(COUNT) has notreached the determination threshold M, the process advances to S145.

In S145, the control unit 120 determines that the termination conditionof the current section is not met yet. On the other hand, in S146, thecontrol unit 120 determines that the termination condition of thecurrent section is met. Then, the termination determination processshown in FIG. 21 ends.

<4-5. Termination Determination Process (Section S3)>

FIG. 22 is a flowchart showing an example of the flow of a terminationdetermination process corresponding to S124 in FIG. 20A or 20B, which isapplicable to the section S3.

First, in S151, the control unit 120 acquires a value currentlyindicated by a timer activated at the start of the current section.Then, in S152, the control unit 120 determines whether a predeterminedtime has elapsed from the start of the current section, based on theacquired value of the timer. The length of the predetermined time may bea time length designated for the current section by the heating profile50. If it is determined that the predetermined time has elapsed, theprocess advances to S157. On the other hand, if it is determined thatthe predetermined time has not elapsed, the process advances to S153.

In S153, the control unit 120 determines whether the corrected indexvalue of the second temperature index has reached a target value. If thecorrected index value has reached the target value, the process advancesto S154. On the other hand, if the corrected index value has not reachedthe target value, the process advances to S156.

In S154, the control unit 120 adds 1 to (increments) the counterN_(COUNT). Then, S155, the control unit 120 determines whether thecounter N_(COUNT) has reached the determination threshold M. If thecounter N_(COUNT) has reached the determination threshold M, the processadvances to S157. On the other hand, if the counter N_(COUNT) has notreached the determination threshold M, the process advances to S156.

In S156, the control unit 120 determines that the termination conditionof the current section is not met yet. On the other hand, in S157, thecontrol unit 120 determines that the termination condition of thecurrent section is met. Then, the termination determination processshown in FIG. 22 ends.

<4-6. Control Parameter Selection Process (Section S4)>

FIG. 23 is a flowchart showing an example of the flow of a controlparameter selection process that can be executed at the beginning (forexample, S112 in FIG. 19 ) of the section S4 in the above-describedthird modification.

First, in S161, the control unit 120 acquires the first temperatureindex based on the electrical resistance value of the heating unit 130by using the measurement circuit 150. Then, in S162, the control unit120 acquires a control threshold equal to the product of the targetvalue of temperature control in the current section and a coefficientrepresenting an allowable deviation.

Then, in S163, the control unit 120 determines whether the index valueof the first temperature index is equal to or larger than the controlthreshold. If the index value of the first temperature index is smallerthan the control threshold, the control unit 120 sets, in S164, controlparameters for PID control of the current section based on a firstcontrol parameter set for recovering the temperature of the heating unit130. On the other hand, if the index value of the first temperatureindex is equal to or larger than the control threshold, the control unit120 sets, in S165, control parameters for PID control of the currentsection based on a second control parameter set for maintaining thetemperature of the heating unit 130. In this step, the control unit 120may also reset the target value of temperature control of the currentsection to the current temperature of the heating unit 130.

5. SUMMARY

The various embodiments and modifications of this disclosure have beenexplained so far with reference to FIGS. 1 to 23 . An aerosol generatingdevice according to an embodiment of this disclosure includes

-   -   a heating unit configured to generate aerosol by heating an        aerosol source,    -   a power supply configured to supply electric power to the        heating unit,    -   a thermistor configured to output a value depending on a        temperature of the heating unit, and    -   a control unit configured to control the supply of electric        power from the power supply to the heating unit in accordance        with a control sequence including at least        -   a first section in which electric power is supplied from the            power supply to the heating unit by setting a target value            of temperature control of the heating unit at a value            corresponding to a first temperature,        -   a second section which follows the first section and in            which the supply of electric power from the power supply to            the heating unit is stopped so that the temperature of the            heating unit falls toward a second temperature lower than            the first temperature, and        -   a third section which follows the second section and in            which electric power is supplied from the power supply to            the heating unit.    -   The control unit        -   controls the supply of electric power from the power supply            by using a first temperature index based on an electrical            resistance value of the heating unit, in the first section            and the third section, and        -   the control unit determines a timing to terminate the second            section by using a second temperature index based on the            output value from the thermistor.

According to this configuration, in the second section for dropping thetemperature of the heating unit toward the second temperature, no pulseneeds to be applied to the heating unit in order to measure thetemperature, so it is possible to completely stop the supply of electricpower from the power supply to the heating unit to cause the temperatureof the heating unit to efficiently reach the second temperature. Sincethe arrival at the target temperature in the second section isdetermined based on the output value from the thermistor, the timing totransition from the second section to the third section is not missedeven without applying any pulse to the heating unit. Also, in thesection in which heating is not stopped, the supply of electric power iscontrolled by using a temperature index based on the electricalresistance value of the heating unit. This makes it possible to wellmaintain the followability of the measured temperature to the realtemperature in order to perform temperature control.

An aerosol generating device according to another embodiment of thisdisclosure includes

-   -   a heating unit configured to generate aerosol by heating an        aerosol source,    -   a power supply configured to supply electric power to the        heating unit, and    -   a control unit configured to control the supply of electric        power from the power supply to the heating unit by using a        temperature index related to a temperature of the heating unit,        in accordance with a control sequence including a plurality of        sections.    -   The control sequence is described by structuralized data        containing a first information element that designates, from a        plurality of control methods, a control method to be applied to        temperature control in each section, and    -   the plurality of control methods include a first method for        performing feedback control using the temperature index, and a        second method for stopping the supply of electric current from        the power supply to the heating unit.

According to this configuration, even after the control behavior oftemperature control are once tuned, it is possible to rewrite thecontents of the control sequence, and flexibly change when to applyrespective control methods to temperature control. This can suppress anincrease in cost caused by trial and error when designing the controlsequence, and makes it easy to switch the behavior of temperaturecontrol to an optimum one when, for example, the environment has changedor the type of tobacco article has changed.

An aerosol generating device according to still another embodiment ofthis disclosure includes

-   -   a heating unit configured to generate aerosol by heating an        aerosol source,    -   a power supply configured to supply electric power to the        heating unit, and    -   a control unit configured to control the supply of electric        power from the power supply to the heating unit, in accordance        with a control sequence including a plurality of sections that        include        -   a first section for changing the temperature of the heating            unit from a first temperature to a second temperature, and        -   a second section, which follows the first section, for            maintaining the temperature of the heating unit.    -   The control sequence designates a first time length for the        first section, and a second time length for the second section,    -   the control unit terminates the first section when the        temperature of the heating unit has reached the second        temperature, and    -   in a case of terminating the first section earlier than a first        time point at which the first time length elapses from the start        of the first section, the control unit continues the second        section over a total time of a residual time until the first        time point and the second time length.

According to this configuration, even when a time shorter than the firsttime length is necessary to change the temperature of the heating unitto the second temperature in the first section, a time during which theuser can enjoy inhalation is compensated for by the residual time of thefirst section. Accordingly, it is possible to maintain adequatetemperature control and avoid a situation in which early termination ofthe session spoils the user experience at the same time.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments with various modifications suited to the particularuse contemplated. It is intended that the scope of the invention bedefined by the following claims and their equivalents.

What is claimed is:
 1. An aerosol generating device comprising: a heating unit configured to generate aerosol by heating an aerosol source; a power supply configured to supply electric power to the heating unit; and a control unit configured to control the supply of electric power from the power supply to the heating unit in accordance with a control sequence that consists of a plurality of sections including: a first section for changing a temperature of the heating unit from a first temperature toward a second temperature, and a second section, which follows the first section, for maintaining the temperature of the heating unit, wherein the control sequence designates a first time length for the first section and a second time length for the second section, the control unit is configured to terminate the first section when the temperature of the heating unit has reached the second temperature, and the control unit is configured to, in a case of terminating the first section earlier than a first time point at which the first time length elapses from the start of the first section, continue the second section over a total time of a residual time until the first time point and the second time length.
 2. The aerosol generating device according to claim 1, wherein the second temperature is lower than the first temperature, and the control unit is configured to stop, in the first section, the supply of electric power from the power supply to the heating unit so that the temperature of the heating unit falls toward the second temperature.
 3. The aerosol generating device according to claim 1, wherein the control unit is configured to, in a case of terminating the first section later than the first time point, continue the second section over a time obtained by subtracting, from the second time length, an overtime with respect to the first time point.
 4. The aerosol generating device according to claim 3, wherein the control sequence further includes a third section, which follows the second section, for changing the temperature of the heating unit to a third temperature, and the control unit is configured to, in a case where the first section is terminated later than the first time point and an overtime with respect to the first time point is larger than the second time length, skip the second section after termination of the first section to transition to the third section.
 5. The aerosol generating device according to claim 4, wherein the control sequence designates a third time length for the third section, and the control unit is configured to, in a case of terminating the first section later than a second time point at which the first time length and then the second time length elapse from the start of the first section, continue the third section over a time obtained by subtracting, from the third time length, an overtime with respect to the second time point.
 6. The aerosol generating device according to claim 4, wherein the third temperature is higher than the second temperature, and the control unit is configured to control, in the third section, the supply of electric power from the power supply to the heating unit such that the temperature of the heating unit is raised toward the third temperature.
 7. The aerosol generating device according to claim 1, wherein the control unit is configured to: terminate the first section when the first time length elapses from the start of the first section, and set a target value of temperature control of the heating unit in the second section based on the temperature of the heating unit at a point in time when the first section is terminated.
 8. The aerosol generating device according to claim 7, wherein the control unit is configured to: in a case where the temperature of the heating unit at the point in time when the first section is terminated is a fourth temperature higher than the second temperature, set the target value of temperature control of the heating unit in the second section to a value corresponding to the fourth temperature, and in a case where the temperature of the heating unit at the point in time when the first section is terminated is a fifth temperature equal to or lower than the second temperature, set the target value of temperature control of the heating unit in the second section to a value corresponding to the second temperature.
 9. The aerosol generating device according to claim 1, wherein the control sequence further includes one or more preceding sections that precede the first section, and a time length of at least one of the one or more preceding sections is variable.
 10. A control method for controlling generation of aerosol in an aerosol generating device, wherein the aerosol generating device includes a heating unit configured to generate aerosol by heating an aerosol source, and a power supply configured to supply electric power to the heating unit, the control method comprising: obtaining a control sequence that consists of a plurality of sections, the control sequence designating a first time length for a first section and a second time length for a second section that follows the first section; in the first section, changing a temperature of the heating unit from a first temperature toward a second temperature; when the temperature of the heating unit has reached the second temperature, terminating the first section; in a case of terminating the first section earlier than a first time point at which the first time length elapses from the start of the first section, maintaining the temperature of the heating unit in the second section while causing the second section to continue over a total time of a residual time until the first time point and the second time length.
 11. A non-transitory computer-readable storage medium having stored therein a computer program for controlling generation of aerosol in an aerosol generating device, wherein the aerosol generating device includes a heating unit configured to generate aerosol by heating an aerosol source, and a power supply configured to supply electric power to the heating unit, and the computer program, when executed by a processor of the aerosol generating device, causes the processor to: obtain a control sequence that consists of a plurality of sections, the control sequence designating a first time length for a first section and a second time length for a second section that follows the first section; in the first section, change a temperature of the heating unit from a first temperature toward a second temperature; when the temperature of the heating unit has reached the second temperature, terminate the first section; in a case of terminating the first section earlier than a first time point at which the first time length elapses from the start of the first section, maintain the temperature of the heating unit in the second section while causing the second section to continue over a total time of a residual time until the first time point and the second time length. 